You need a *standard* 130mm BCD Shimano Hollowtech 2 crank for a road bike... in your case, a triple if you want to swap rings. I'd just buy a new crank unless you find someone that wants to trade.

Basically, any standard HT2 road crank (with rings) will work with your frame and bottom-bracket, double or triple, black or silver.

Just buy a full crank with rings, unless you happen to find some compatible arms on ebay; it will still likely be cheaper to buy the whole crank with rings; then you have extra rings.

Post a link of what you found, if you want confirmation.