It looks like a very small accumulator to dampen "hammer" when a faucet is opened. Any residential plastic accumulator will work or you can just install a tube about 12" tall with a cap on it and leave air inside and it will also do the job.

It looks just like the water filter that I replaced on my '75 Barth, mine was black plastic and the replacement cost about 4 bucks.

Man
Sharkbite fittings are an arm and a leg I dropped over $200.00 bucks on a little job.Hopping I over bought and will have a return.
PeterMac

I found q number of suppliers on eBay for Sharkbite connectors. In small quantities some were under $2 each (and some as much as $100). Have you looked at eBay?

Thanks Tom I will look now however the damage is done. But for the next project.