I didn't see sand toys on board the Conquest, but we did buy some from a vendor at Playa Mia in Cozumel. I think we paid $8 for a mesh bag with 1 or 2 buckets, a shovel, a watering can and maybe one other thing. They were asking $10 and we couldn't get them below $8. Personally, I think $8 is too much considering you can get them so cheap at Target or Walmart, especially at the end of the season. Next time I would make room for them in my luggage. Hope this helps.
I agree with OhioT's.........go to the dollar store or another discount store. You just need a few things. You can leave them on the beach at your last port so you have room in your suitcases coming home. We did this in Mazatlan with inflatable mats. I bought a couple of mats at the dollar store then left them with a family that was spending the week there.