Hi James
It’s straightforward to raise the seat, you just need some spacers and longer 8mm set screws. Experiment with bits of 2 x 2, or similar, with a 9/10mm hole drilled through them. When/if you arrive at a satisfactory size for the spacer then get it made in metal.
Looking at the parts books the same handlebars were fitted to the TS 125/150 and the TS250. I have bikes with both handlebars and will measure them on Sunday and let you know. At a guess I would say that the grip area is a couple of inches higher and a couple of inches further out.
The handlebar is a standard size so bars off other makes will fit, you will only need to drill and tap a hole for the “choke” lever.
Brian