Easy solution: buy a round-to-square converstion grip. Will result in the exact same profile as a SB frame. A set of Hogues will set you back about $16, custom grips can run $200+, and every thing in between. All the mfgrs offer them.
Kernel is correct. The conversion grips will feel exactly the same in your hand. I have Houge, Ahrends, Altamont and Herrett's wood conversion grips and all look and feel just great.