I spoke to one plumber who thought it very unlikely there would be enough water pressure that high up to be able to put a shower in.
Architects that design tall buildings are paid to anticipate such problems and will have something in place to avoid such low water pressure problems. Such low water pressure in tall buildings would also mean it would take a much longer time to fill your bathtub or for your toilet tank to refill after a flush.
How's the water pressure at the bath tub spout and bathroom sink? Is it much the same as the water pressure in any faucet in any restaurant washroom or in the washroom at work?
If so, you can just replace your existing bathtub spout with one that accomodates a hand shower, like this one:
You just connect the hand shower to the threaded nipple on the spout, and mount the hand shower in a holder where a shower head would typically be.
Look on the bottom of your existing bathtub spout right near the wall and see if you can find a set screw holding the spout on. If you find such a set screw, then you have a "slip on" spout, and you remove it by loosening that set screw and pulling the spout off of a short piece of copper pipe sticking out of the wall. If there is no set screw, you remove the spout by unscrewing it.
If you have a slip-on spout, then phone Moen customer service and ask if they sell a diverter spout identical to the Moen 3931, but with a hand held shower attachment. Alternatively, ask if they have a "screw on" spout identical to the 3926 with a hand held shower attachment.
The Moen 3931 has three features that make it superior to every other slip on spout I know of:
1) It has a "cup seal" (aka: "cup washer") in the diverter gate that "inflates" with water when you pull up the diverter. As the cup washer inflates, it seals against the end of the copper supply pipe so that NO water leaks out of the spout while the shower is on. Not a drop! That ensures you get the highest water flow rate out of the shower head for the best shower performance. The 3926 is the same in this respect.
2) It has a "yoke" which clamps around the copper pipe rather than a set screw that just tightens up against the copper pipe. This yoke distributes the tightening force much more uniformly around the entire circumference of the copper pipe, thereby greatly lessening the liklihood of damaging the copper pipe with the set screw.
3) A "repair kit" for the Moen 3931 is available free of charge for the Moen 3931 in case the cup washer ever needs replacing. Just ask for Moen Part # 10644. (it also fits the 3926)
Product Detail: 10644
The above web page says the suggested list price on the repair kit is $11.65, but if you phone Moen and tell them the cup washer is torn, they'll send you a repair kit free.
If you see Moen diverter spouts for sale in your local hardware store, check to see that the name "Moen" is molded right into the plastic the spout is made of. If you don't see that name, then the spout is made offshore (in China) and doesn't have that patented "cup washer" in it, and won't work as well as one that does. That is, lots of water will spill out the tub spout when you're having a shower.