You'll just have to look around. I got four GE red-etch ones at a ReStore a while back, though all but one have since gone EOL and the remaining one is on its last leg. I saw some Philips ones at another ReStore more recently but I didn't buy them and they have all since sold.
As far as a fixture goes, Lowe's and Home Depot sell junky T12 shoplights for about $10 and somewhat-nicer T12 striplights for $20 (unless they've discontinued them recently). Those would work if you don't mind electronic ballasts. If you'd prefer magnetic RS, check Craigslist or ReStores. There are PLENTY of 4-foot T12 RS fixtures out there.
I still have my 2 F40T12 magnetic RS fixture, but it seems like the problems have come back.