Do you mean the bolt that holds the crank arm on has stripped in the bottom bracket axle? There are no threads on the chainset other than the one around the bolt hole which holds on the cover and is used to thread in an extractor plus of course the pedals the other end. So you could just need a BB axle not a complete chainset.
If you're not worried about keeping it period correct any 42/52 (or any other tooth combination) chainset will do, you'll also need a square taper BB as well if the tread has gone.
You could upgrade to a modern Shimano Hollowtech chainset which will come with a BB.
Otherwise look for a period Raleigh chainset used on
eBay or ask on here, I'm sure someone has one kicking around.
BTW welcome to the forum 😊