Nelson Nelsplats are the right size, just try some smaller sizes and match to the bore.
I wanted a better barrel, and cheap. I got on Ebay and saw a four piece kit for $32. I got three fronts, and one back for $32. That cannot be beaten. I got it and put my CO2 on, got some paintballs, and tried it out. It was extremely accurate, I can hit a telephone pole from around 50 Ft. It is also more quiet than any other barrels I have used.
This barrel is awesome. I could not be more happy. For $30 it is worth a try.