Interesting, lani. A couple things I will throw out there:
1. Not all rep Rolex magnifiers are the same. Measure the diameter from flat side to flat side. The old "Noobmariner" subs, for example, had magnifiers that were too wide compared to gen in this dimension.
2. A mass produced sapphire magnifier of these dimensions should cost no more than $10 USD. Small custom jobs would be much higher, and you'd probably be looking at $25 minimum anyhow. So that would mean 0 savings over this crystal magnifier combo. But I could swear that loose magnifiers used to be available on Ebay and elsewhere. What about Ofrei? They used to sell generic Rolex crystal parts?