I bought these. Seen okay, but the kegs haven't seen beer yet. $5.99 for 5 kegs.
https://www.amazon.com/dp/B0105JJ8L2
For 6 bucks that is a steal. I remember when getting rings and parts were pricey but now they are all over the place. I bought a 4 pack of SS PRVs a week back for about 12 bucks. It used to cost that much for one plastic one.