+1 for Chile forge. I bought their burners and made my own forge.
Do some more research on blown forges.
I dont know what you want to invest $$ wise, but a lot of us knife mamkers make their own blown gas forges for less than $100 each.
Basicly you need a container (pipe) to hold the refractory (insawool) and a blower with some piping and a regulator.
The next one Im building will be with a pre cast hard refractory liner from these guys http://www.hitempincusa.com/firebricks.asp.
There are a couple of tutorials over on knifedogs that cover it in much more depth.
I have a Chile Forge Habanero with the old style burners and it gets plenty hot enough to forge weld a 6 x 1.5 x 2.5-3 inch stack of 1084 and 15N20. Their new models come with the new, improved burners and bigger openings so you can get a bigger billet into them. I have been happy with mine. With that said, my next forge is going to be a round 12 inch blown vertical forge or one that is stretched to 16 inches long like Ed Caffreys big forge and will be specifically for forge welding. You can put crushed up soft fire bricks in the bottom and when they get too much flux on them, you just dump them out and put new brick bits in. IMO, flux is the biggest problem you will have with any forge.