Good luck PC...
Getting somthing for a BMX that is not 20" can be a bitch...
I tried upgrading my lads 18 inch BMX wheels this summer. We found something but they didn't fit in his drop outs, then found some rims online but this means we are stuck with the old hubs, the local bike shop drew a blank so we have temporarily given up unless we spend more than the bike is worth.
I think you have a harder task ahead of you with 24's and anything that can be classed as 'old skool' will have a heavily inflated price tag.
BTW great pics, looks good for a bigger bike and a great restoration job 8)
Whats up with the current wheels?