You need a DC voltmeter, not a "tube meter.". Radio Shack has them. Ask them for a DVM or a multimeter. It will be able to measure AC voltage, DC voltage and resistance. Set it to DC volts and you are in business.
IMHO, for this application, you can simply get a multimeter from Radio Shack or Sears. I have been happy with Fluke and HP products, but if this is your only use of it, I recommend getting something inexpensive. There is not much to be gained by purchasing and expensive multimeter for tube biasing only.
the $8 meter from Harbor Freight works great for biasing amps. If you spend more than that for a meter, make sure it has auto range detection, otherwise it's not worth the extra $'s. I picked up a couple of the HF meters for $4 each off of a sale table. They're also great to have around for other purposes. I've also seen the cheapo meters sold on line by MCM and other places. You can order from Harbor Freight online too.