Theoretically the all alloy Yamaha Zetec S should fit in the Coupé as it's a narrower engine but they are still a bit pricy second hand except for the 1.25l version for me to get one for my saloon.

Your other option is to get a ZVH based engine, this gives you the stronger bigger capacity bottom end of the Zetec with none of the fitting problems of the full Zetec. Because of the modifications done to the Zetec block to make it take the CVH head it also reduces the width of the engine. It's the water pump and wide flat belt on the Zetec that makes it too wide for the saloon, the bare Zetec block is exactly the same width as the CVH.

There are several people on ebay selling ZVH bottom ends or complete engines, one owner has recently bought a 1.8 ZVH for a good price on ebay. The 1.8's are a lot cheaper as everybody wants the 2.0 Make sure you check if it's for a turbo or not if you buy one as the compression ratios will be different and a turbo block should have a oil return from the turbo.

Obviously the CVH engines all fit as these are standard for the Coupé and in the XR2 donor.