Looks to me like a regular 5k burst disc. Looks exactly like the one on my little air tank. The manual only tells you it’s a 10 mm head. I have some generic ones on order just to have. They should be here Friday and I’ll let you know for sure. You could email hill and ask the question. [email protected]
Another alternative would be Air Venturi since they are the main U.S. distributor. Although, in the past, Hill has been very responsive to e-mail queries, so they may respond faster.
Got these in today Captain O-Ring HPA Burst Disk 5k - 2 Pack (Compressed Air Tank Paintball) [Bonus CO Microfiber Cloth] got them off Amazon. Used a 10 mm socket removed the factory 5k burst disc and installed the new one. Only filled a few times but it holds air and fills up the guns just fine. So after this I would fill safe to say that any 5k burst disc that you can find online for an air tank will work. I do like the captain o ring ones they look quality. And come with a micro fiber towel!