Some RC ships have actual dive shops, some do not. Those that do, sell Suunto computers. If you are interested in buying one there, check out prices at home before you go so you have an idea what is a good price.
My husband and I ended up buying our Suunto Mosquitos on a RCCL ship a year ago. On our first dive of the trip our computers failed (after having just been serviced!). Luckily we had back up bottom timers and depth gauges, so we could finish the dive. Later we rented computers from the ship's dive shop, and were told that if we wanted to buy computers they would take off the rental fees from the price. We tried them, did some online research, and ended up buying Mosquitos for a good price. We have been happy with them, and our old computers are now backups (redundancy is good!)
Do your research before you go, then you can decide whether they have what you want at a good price.
And yes, our LDS did take care of our failed computers once we got home, since they had flooded immediately after servicing.