Amazing how you find a thread just as you need one. I just received email from Pinball Resource about this very topic - I need 16 new reel guides for a machine I'm restoring, which also happens to be a Big Top. They don't have them.
The originals are effectively dust; I don't have a single guide that's fully intact. If I did, I was going to try casting some using molding materials from Smooth-On, but the kit that would do what I need is going to cost about $70. Kind of steep for making a handful of card guides.
The problem with using the Newark guides is that in the middle mounting plate, you've got guides attached to both the top and the bottom and the guides mount with a stud that fits in the hole. It's not possible for both the top and bottom rails to mount in the same hole, so you'll have to offset one of them slightly.
After checking the item at Digikey that Model237 mentioned (PCG-4A-48), I found this, which looks like a very close approximation of the original Gottlieb part:
It's adhesive mounted, and has an offset mount like the original part. It comes in 4 foot pieces, so it will have to be cut down.
The problem is that hardly anyone keeps that part (Richco/Essentra PCG-3A-48) in stock, and many that do have ridiculous minimum order requirements. Allied Electronics told me I'd have to order 1000 of them.
Bisco (Biscoind.com) stocks them, but they've got a $25 minimum order. Plus shipping. Plus handling. I needed two four foot units that retail for $4.38 each, and ended up having to spend $37 to get them. I bought some, and if they work out, I'll post the results.
PBR really needs to reproduce these...