The only real alternative to a B or C Hammond (my opinion - your opinion may differ and I may be wrong!) is the Korg BX3. But then it doesn't have pedals. So you could get a full MIDI pedal board from Speakeasy Music. The problem with this is that you will spend as much or more for this rig than for a good used A-100 and Leslie.
You might find a used Lowrey or Thomas, etc, for a low price that would have built-in speakers and full pedals. This could be a very affordable alternative.
In the early 1970's my mother had a Gulbranson (Rialto model I think). Full pedals, drawbar section and built-in Leslie. Nice organ.
A different alternative might be an older Hammond. It might have the ratchet-type drawbars, no percussion, and no scanner (or some combination of this stuff), but these organs are servicable and could be an inexpensive practice instrument. You would still need a Leslie with these. Possible models: A, B, BC, BV, B2, C, C2, D, or E. Before buying an old instrument, I would always inspect it and play it before purchasing. (And know a reputable local service guy.)
I hope this helps.