search on sport courts. They're typically some sort of a resilient covering over a concrete slab.

yeah, but -- I only need like a 3x5 area. Not sure that would be appropriate for what I want. Thank you for the response!

That's a pretty small area , I'm suprised that you can't get the rubber mats to stay stuck together. You might try gluing them down to a full size matt.
You'll be able to find a wide variety of matt surfaces at a carpet remnant store.

We routinely use these inexpensive rubber 'click together' mats that have been glued to pre-fab concrete stepping stone slabs under childrens swing sets and at the bottom of slides, it keeps the mulch from wearing out in those areas. I've also glued them to marine grade plywood . They area as cheap as you are going to find.

Another option would be to use Ecosurface- but their minimum size roll is 4ft. x 25ft and it is not cheap, but it makes a GREAT looking surface on a floor on an outdoor rooftop deck or in the garage.

In my own back yard I purchased a very inexpensive outdoor rated ( woven from recycled plastic bags) carpet to put over a concrete patio. Works like a charm. It would be even more bouncier if I had some of those rubber mats underneath it. They come in all sizes too .
Google "outdoor carpets".

6' x 4' rubber cow mats or horse stall mats are listed online for about $45 or can be picked up at a farm supply store. (I use one for dampening the vibration of my washer and dryer on a tile floor.)

these are some good ideas -- thank you. I'm so sore and hurting today from dancing on concrete last night! The old bones can't take that anymore!