If you buy a strait stitch machine and mount it on a longarm table you can get a stitch regulator for $500.
I have the Baby Lock Jane which is the same machine as the Brother 1500. I added the stitch regulator and it works very well on my long arm table.
Other wise the only stitch regulator is on the Bernina.
I have seen the Fabric Mover type attachment that has the opening that you stitch inside. It came out years ago. But it is not very well liked and the price came down. But havnt heard much about it anymore.