You can get a 5' "soaker" tub with wider stance and deeper seat for about $200. For a 5' jacuzzi (check out the one fifth on the list), it'll run you about $800. Both take only a couple of inches either direction than a "standard size" tub.

Handshowers that come with Roman tub faucets are not for use in a shower situation with a drop in tub. They are for cleaning the tub or rinsing shampoo out of the hair of a seated bather. If you wanted a tub/shower unit, you would have needed to have designed the installation as such from the beginning and used a tub that was designed with an integral tile flange and then used a wall mounted tub/shower type of faucet instead of a deck mounted Roman tub faucet. Those tub/shower types of whirlpools are usually designed for alcove installation where a glass door can work with them just fine. But, since you've already put in what you have, the only way to use safely such a tub as a shower without setting yourself up for a lot of water damage is to do a "ring" shower curtain like you would for the old fashioned claw foot tubs. It's basically a rectangular suspended curtain rod that you use shower curtains with. A glass door of any variety will not work in your situation, as it will not keep the water off of the tub deck and walls, which is the big danger with using a drop in tub in such a situation. The water that splashes on to the walls and deck has no way to drain back into the tub because the lip of the drop in interferes. The water has to go somewhere, and that usually is your floor or into the walls and deck surround. This makes for a nasty moldy rotten mess in a few years.

Just go buy something at Lowe's or Depot. They have the some darn plastic stuff.

How imminent is possible resale? What are typical buyers' family make-ups in your area? Are no-tub homes common in your area? Is it a buyers' or sellers' market? Unless resale is in under 5 years, average age of kids in the neighbourhood is under 10, everyone has tubs, and it's a buyer's market, which is an unlikely combo, LOSE the tub. Too many people hang on to them because it's believed we 'should'. A good walk-in shower with a built-in seat and large enough for a wheelchair is far more versatile and practical. It's not just stepping over the tub rim that makes people want to get rid of them. Tubs are far smaller, often messier, & less commfortable overall. And you have an outdoors one for the luxury aspect. We need to LIVE in our homes fully, not under the shadows preceeding future owners :)