Try some local hardware stores or some hobby shops. It is a regular M3x3mm set screw. You can also try aliexpress or similar.

Regular checks are probably the best. And not just of the plunger. Try to check every single screw on all of your gear regularly and see which ones you need to check more often and which ones less often. Check even those screws you don't use to adjust/tune. Screws on your finger tab can get loose as the leather works and deforms... the screw on the limb itself that holds the spring detent for the connection to the riser. Looking for these small parts in grass is no fun .
Check also all moving parts... if you have magnetic arm arrow rest that it swings and returns freely and the plunger tip moves smoothly inside the barrel of the plunger.

You can try to put a little bit of wax into the threads of these 2 set screws on shibuya plunger to make them sticky and less likely to get loose. In these parts the wax shouldn't get to the spring/barrel and interfere there.

 

This

It is a regular M3x3mm set screw.

I'd be very careful about using the correct screw. Given that what your screwing into is aluminum and only has a few threads it would be easy to damage the threads with the wrong one.

 

To follow up on securing the setscrew, Loctite and many other thread lock companies sell a low strength thread locker, its purple. You can apply it as well, first start the setscrew then place a dab on the remaining threads before making it up all the way. The Low strength of these are specific to threads smaller than 6mm / 1/4"

 

Hobby shops that specialize in remote control cars/planes/boats will likely have what you are looking for. I'm not sure if that is a regular size for drones.

For non-local, there is always McMaster-Carrs and Grainger, but the shipping may or may not be as prohibitive as Lancaster.

 

I'm like 86% sure that the lock screws in lapel pins are the same as the lock screws in plungers (at least the WNS ones). I haven't 100% checked it out, but I can do it tonight. Bought the lapel pins on amazon to secure my kids usa archery pins. That being said I've had at least 3 archers lose a set screw out of a plunger, so I've had it on my pad to check it out.

 

McMaster Carr sells it all

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

Shibuya parts diagram says it’s a hollow 3mm x3mm so I think you’re safe Which mysterious matches the set screw that needs a 1.5mm allen wrench.

https://www.shibuya-archery.com/media/dxplunger_1.pdf

Stretch

 

This is exactly why I am curious to know if people have had any issues with random set screw brands. Also if the screws are listed in imperial rather than metric, will they be suitable? McMaster-Carr lists hollow screws such as 1/8" 10-24 so how do I convert 3mmx3mm?

 

Imperial threads are not compatible with metric threads, so don't try to mix them. M3x3 is the correct size for that set screw. This is also the size used in Shibuya Ultima arrow rests. McMaster is a good source. So is Amazon. You can even get a set with all different sizes for potential future needs.

Amazon.com: uxcell 50Pcs M3 x 3mm Stainless Steel Hex Socket Set Grub Screws Headless Cup Point : Industrial & Scientific

Amazon.com: uxcell 50Pcs M3 x 3mm Stainless Steel Hex Socket Set Grub Screws Headless Cup Point : Industrial & Scientific

www.amazon.com

 

Thanks, I suspected that was the case not to mix metric and imperial.

 

Bolt Depot is where I get this stuff. 100 for less than 7 dollars last time I ordered. I generally buy several different things to make the shipping a bit more efficient.

Bolt Depot - Metric set screws, Allen, Dog point, Stainless steel 18-8 (A-2), 3mm x 0.5mm

boltdepot.com