If you prefer mouth2lung, have a standard grand with the older contacts, and want to stay around $40, the closest fit from Rob's stable would be the RM3 or the IGO-S.
They're small (fit the catch cup) and can be run with single
coils (single coil version of the RM3). They're great for M2L draws and give great flavour like the RM2. With the single coils, you prolly wouldn't stress the limits of the old contacts and button, per FB above.
If you wanted to try your hand at dual coils, you could get the dual coil version of the RM3 - just stay at .6ohms net and above and you shouldn't stress the contacts too much - just keep them clean and apply noalox (the grey goop you got with the RM2).
Larger diameter atties like the RM4/5/6, or non-Rob atties like the Odin won't fit with your catch cup.