Anyone know what a reasonable price is for a Westinghouse circlarc tube and a Maxilume circlarc ceiling fixture?  There is some on eBay right now and I'm interested but don't want to overpay. Thanks for any info.

The fixtures certainly aren't common, but working lamps are exceptionally rare. I can only name one member here (DieselNut) who has one, but there may be someone else too. I found the fixture and lamp that you mentioned on eBay, and the BIN price for the fixture is reasonable, I'd say. The lamp is auction-only, and there's no telling how high the bids will go. Personally, I wouldn't pay more than $50 for a working lamp, shipping included, and even that's pushing it. I do know that the lamps haven't been made since the early 50s or so, and NO modern lamp is a good replacement. The closest you can get is a Circline. As you probably know, Circlarc stuff is too rare to use for lighting anymore; it really is museum material at this point.

I saw those and was interested in the lamps, as I only have one working one and one EOL one, but have three dual tube fixtures (similar to the one that was in the auction).  I would be willing to trade someone a fixture or two for some NOS tubes.

I've never seen either the lamps or the fixtures anywhere but on LG. Oh well, just another reason to get up early on the weekends to hit the flea markets...