Try eBay. Also, Google "T5 fluorescent bulbs." There are lots available online.

Hope this helps.

I should be more clear, the bulbs are easy to find on the internet and quite inexpensive but the fixtures seem outrageous compared to t8/12s.

Agreed, most of the fixtures you find are a ridiculous price. There is nothing significantly different between an electronic T5 and T8 ballast. The "hydro" stores are just ripping you off. In the UK, T5 ballasts are available for only a little more than T8 ballasts if you know where to look.

I found a website that said the guy ran 54w T5 bulbs from SL15 ballasts? Is this correct? Could I buy the SL15 to run T5s instead of purchasing the $24 T5 ballast?

Thank you

Here is a link that might be useful: Overdrive Link

Modern electronic ballasts are very flexible and will regulate current through a wide variety of different fluorescent tubes to the extent that they will light up. Many of them are even designed to do this, correctly operating different tubes in a variety of powers and even some compact fluorescents. However, there is a different current that is intended to run through each sized tube so you will not be running the tube at spec. A T5HO tube is designed to run on a higher current than, for example, a standard T12 and would be underdriven by a T12 ballast. Underdriving would be a bit of a waste of time. Overdriving a T5HO tube is not a great idea since they are already overdriven. Also the starting regime could be wrong, contributing further to damaging the tubes.