Where to buy?

Purchasing a jamb peg. There's not a lot of choice

The industrial jamb peg manufactured by BHandasa is available, the motor is 3 Phase and has a speed control. Top of the range.
There are a few styles of jamb peg machines around, but unfortunately most of them are not commercially available.
Be wary of the cheap jamb pegs online. I see a couple with the table attachment but most of them are without any method of cutting tables.
The table attachment which is a must have for a hobby cutter, makes cutting so much easier.

The FraLap is a traditional French jamb peg, check it out: FraLap

The two most affordable machines would be the traditional French jamb peg and the Som jamb peg, which I refer to as a modern jam peg manufactured by Kalpana Machine Tools
I have provided links below. I now have a Som jamb peg and the quadrant is very well built, no complaints at all. See the next page for more information.
Except for the base, the Bhandasa and Som faceting head are almost identical.
Keep in mind that a good quality jamb peg is a one time investment.

The SOM Head

If you have your base then this would be a good option, but you will need reverse to use the table attachment. If I bought any one of these machines I would also purchase extra standard dopsticks. 8 sided and 6 sided for triliants, you can't have too many.
Take a look here

The SOM desktop

The Som appears to be a hobby cutters machine, not too big and portable. Compare the setup to the Bhram, notice the arm rest? If I had this machine I would figure out some way to make an arm rest. This would give you much better control over your cutting Take a look here

The Brahm jamb peg

The Brahm is an industrial system. Has a 3 phase motor with speed control and mounted in a table. For a serious gem cutter this would be my choice. Take a look here