Hey diapered daughter,
If you are a bit handy and creative you can build a BIG BABY crib out of PVC pipe. Its pretty reasonable pricewise and it's available at all the big box stores like Lowes, Home Depot or any lumber yard. A cheap hacksaw, tape measure and glue is all you need for tools.
4" pipe for corners and mattress supports (use 4 lengthwise). and a piece of 1/2 plywood over them for the mattress support.
2" for cross bars and 11/2" for the vertical bars.Use T fittings or L fittings to join the pieces and caps to finish the posts. Where two different sizes meet you put a reducer bushing in the the T where size changes. You can ask the store clerk if you have any questions about how to use the stuff, but it's pretty simple. Stick it all together before you glue it to check that it's what you want because once it's glued it's not coming apart.
Glueing the joints will make it quite sturdy and leaving the joints glue free will make a very effective hinge joint. You can make it storable by not glueing the corner joints and drilling a hole for a metal screw to hold the joints together. Oh yeah, the stuff is pretty light in weight so it makes it easy to move. The stuff paints great with spray paint, so get artistic.....