My solution has been to use a USB wheelmouse which allows me to use both mouse and trackpoint.
Thanks for the thought, Syd! I'll try one of these sometime. (I've been using a good plain old Logitech 3-button PS2 mouse, but it's oldish now and getting "sticky" -- could try cleaning it yet again, though -- and I can't seem to find these in the shops anymore. Wheelmice abound, however!)
And most of them seem to come with a USB plug on the end and a usb->ps2 adaptor (which often seem flaky) so you'll probably have usb anyway :-)
Syd