42t or 44t chainring?

almost all BMX racing chainrings are 110bcd 5 bolt, type in various bmx brands you will get a lot of choice and old school colours.

Sugino BMX, Tioga, FMF, etc etc

They are 1/8th too, same as track chain.

Thanks for the info FP, I hunted one down at Alan's BMX and it arrived today, here's a pic.

All for the princely sum of £6 plus postage.