Pomegranate, Eugenia or Bougainvillea (mentioned above as bougie) may all be good options as well. It sounds like they are avid gardeners so I see no problem with a crab apple and maybe a nice bonsai how-to book to go along with it.
The second photo image you have posted is "Malus Halliana" crab apple - which is owned by Walter Pall I believe. So you have set the bar quite high for yourself. This was imported material if I recall and he spent many years re-growing all of the branches. It is probably one of the best examples of a crab apple that you will ever find - even though you will probably never find another trunk quite as good. The price range you are looking at and the example you have selected are miles apart. I say this only so your expectations are tempered a bit. You can find a decent trunk for $200 I am sure - but nothing like the example you have offered up. If you have time and patience why not buy a few and grow them out. Good luck ...Tom
2 questions if I may, first, fill the tree suffer if left like this over night until I go buy some root cutters in the morning?
1. It is already suffered a pretty horrific day. Don't you think?
2. What did they use at House of Bonsai? Something special or just some pruners and a saw?