Sun International is long since out of business. They used to do a conversion of the 1st gen Elise with a B18C5.

Lotus sells the Elise in other markets with a Rover K-Series engine. Prototype Racing converts Elise-based cars to a Honda K-Series engine but the cars aren't typically street legal.

Lotus just came out with a version of the Elise called the 111R which uses a Toyota 2ZZ-GE engine from the Celica GT-S but it has a Lotus ECU and supposedly puts out 189 hp. It will be on sale in the USA shortly.