I've got one of these. They will run a 35W lamp reasonably well, but a tad underpowered in my opinion. It won't run a 26W lamp though, sorry but I've tried
You won't damage the lamp just trying it, but it won't run up fully.
35W ballasts do turn up on eBay,
this one will run 55W lamps as well. Not the cheapest, though. However quality is always worth paying for, and Parmar ballasts are good.