Actually, building mono coils for the TDI's is fairly easy. I don't recall offhand, but you can measure the inductance, and DC resistance of a factory coil, and match those characteristics with the coil you build. I built a 24" for mine, but rarely use it do it being too cumbersome, though it worked fine for larger relics. I just made a round form out of ABS plastic, and wound the wire on that, and glued up a mount. There are some steps that can be taken to improve performance, that I did not take, but the basic coil is easy. Somewhere on the forum I posted a pic of the connection at the box. Also, you have to research the wire size you need to balance the DC resistance with the inductance. Greater wire length, of a given size, increases resistance, and more turns increases inductance. You should, if you haven't yet, do a bit of research on inductance in coils, especially as it applies to various shapes. On a side note...one coil I made that did not work worth a hoot was a 9" x 18" elliptical. You can scratch that one from your list.....LOL
Another thing I did was make a round form for winding the coils out of a sheet of plywood, and wooden pegs. I drilled holes in the plywood for the pegs. I made some wooden washers, though plastic store-bought would have worked, to slip over the pegs to hold the wire above the plywood, so I could get string around the coil bundle, at each peg to make the coil a whole. Winding is easier if the pegs tilt outwards. The inductance, as I recall, didn't change much by shape. If you know the perimeter length of an elliptical you want, you can wind it as a circle, and then form it into the elliptical shape after.