Actually, the game has changed!
The cheaper solutions are (and have been) available for the E-500 forat least a littlewhile now. Try this link:
VirtualVillage USA on eBay
Their prices went up -- it's now $30 + $7 shipping (used to be mid $20 with free shipping or something similar), but that's still significantly cheaper for split focus screen designed specifically for the E-500.
Dozens of reputable people on other forums (DPReview for one) are recommending them without reservation. I'm getting one based on those recommendations. I will come back to the thread and post a little review when I get it.
Although the E-500 isn't designed for quick changing of the focus screen, it's relatively simple and non-instrusive to do.