12v linear power supply

What amp rating do you need?  If it's for a low power device such as a DAC, then you can get away with a 2A power supply.  I think the best you are going to do is keep your eye out for a used SBooster 12-13V model.  They sometimes are sold in the $300 area.

Otherwise, your only alternative is a Teradak or Zerozone power supply on ebay from China.

Those used sboosters go quick. 

Honestly,  idk about what amps I needed. I thought I was just suppose to look at voltage. 

 Would you be able to build one yourself? AMB has a couple of versions that are very high quality. The completed kit would likely run $100+ and be a reliable and able unit.