Now that's a change...I converted from playing a righty bass strung righty and played upside down (like Jimmy Haslip of the Yellowjackets) to a true left handed instrument. Have sometimes thought about doing what you describe--my left hand has the dexterity to pluck/pick but not to fret, so I get discouraged pretty quickly. Also figure I have too much lefty playing time under my belt to make it worthwhile.
Why the difficulty/expense in getting lefty instruments? Yes it's a pain finding them in music stores, so I took to eBay to do that. So far so good, with only one dud acoustic guitar among the several basses and guitars I've bought that way, all the rest of which have been great players after proper setup.
Praise & Worship Club #903; Fender Jazz Bass Club #860; Hartke Club #164