My friends cat had a limp and we snuck it into work and xrayed it, and found out she had a broken elbow. We used a finger splint from the ER, and splinted her and she is just fine. Could you try a popcisle stick and some tape??
That is what we did, it you know anyone in the medical profession, medical tape would work the best.
Kylie had been limping last week and I snuck her in an xrayed her, (let me tell ya that was fun, about like giving a cat a bath :O !!
) but she is fine now, couldn't have splinted her if my life depended on it!!