Noel Coward once remarked on a opening night of a revue when a dancer hadn't put on his dance belt

"Tell that boy to get the Rockingham Tea service out of his tights!"

I'd reckon a couple of tube socks rolled over "yourself" would look most realistic, ensuring correct postioning and overall squidgy not to bulky OMG that man's got a colostomy...reactions.

Dildo's and such are too firm for your purpose, and imagine the embarrassment if they worked loose down your trouser leg to freedom!

Arrgh!