The reptile lights from the pet store are the cheapest nicest way to go because they are flourscents. You could get UVB out of sun-tan type bulbs or those halagen spot lights, the problem with them will be heat though. The trich's on a plant are a defence system, you can basicly consider them as "sun screen" for weed and the area's of the world that are known for having the best strains/smoke are all areas with higher UVB. Here is quite a nice video about it.
http://www.youtube.com/watch?v=IPcpt3Be28o I also think I remember a post on here somewhere about UVB lighting so you may want to search arround for that also.
You have 2 choices with the reptile lamps, the t-5 20in fixture or a CFL. Here are some that petco sells they are also avaiable at petsmart which i think is where I got mine, its been a while sorry rofl..
http://www.petco.com/Shop/Product.aspx?sku=1128639
http://www.petco.com/Shop/Product.aspx?sku=1128582
I use the T-5 tubes just because the ones I got had a nice reflector built into the fixture and I just think I get better coverage with a 20in tube than I would with the CFL but they were like $10 to $15 bucks more than the cfl if i remember correct. They are both the same wattage and uvb output so if you allready have some sort of reflector to plug a cfl into that should give you nearly if not the same results.
With your small room, yeah may as well start out with just a single 20w uvb bulb and you can always add more later. My experience with it was a noticable differance in quanity and size of trich's, it also felt like they changed color faster but my harvest was not any faster. So I am just thinking it was a quanity thing there more crystals so looked like more going brown faster. I started out with just 1 of those bulbs and after seeing the differance between the plants that were under that uvb bulb I went and got 3 more for my 12x12 room. I could add more to it I am sure. I have experminted and hung those bulbs with in 3 to 6 inches from plants and was not able to cause uvb damage on the plant. Normally I like to have my uvb bulbs about 8 to 10 in above the canopy just to spread that light out more.
I use the uvb light from day one of blooming and have it on a timer with my lights. If you were to add UVB to your current grow you should still see some benifit because you still have about a month to go or so. I am just not sure how much benifit its going to be and I dont want you to try it and not see results so you may as well add the UVB thing to a future grow. But hell if ya got the extra $25 or so then give it a shot. Just dont be so quick to judge it on that current grow make sure you try it out for a full bloom to harvest thing after this grow.