Put up a sketch, or picture with a ruler showing what you really have now. Repairing/replacing this may require bringing up to code. This means you must have 15" from centerline of the toilet on either side, and room in front for your knees when sitting there. In the USA, the 'standard' toilet rough-in is 12", where optional 10, and 14" toilets are also available (they tend to cost more since volume calls for mostly 12"). Whenever you go outside of the 12" rough-in, your choices get smaller.
Some 10" rough-in toilets might work, but we'd need to specifically know what your actual rough-in measurment is. Most toilets normally have at least some space behind them, and if the rough is shorter, that eats up that space. Might fit, might not...for example, the Toto Vespin with the Unifit adapter, typically has 3/4" behind it, so if it was at least 9.25", it could be made to fit. I think the 10" rough Drake has even more room behind normally.