I don't think you'll find anything to bond acrylic to a rubbermaid sump. Once you fill it with water the rubermaid tub will flex outwards and seperate the partition. It's the main draw back of a rubbermaid sump.
I gave up and got an acrylic sump. Be interested to hear how you do with it.
Best thing to install partitions in a rubbermaid is by using smaller containers. As reefland indicated the rubbermaid will flex too much for anything to bond to.
I used a 5g bucket to hold my media inside a 30g rubbermaid sump. Just drilled some holes at teh bottom. It worked great.