Even with ADA, an employer is not required to provide an accommodation if it is too costly for the business.
I will leave aside for the moment whether you disability even qualifies for the restriction ADA definition. For the sake or argument, let's assume that you qualify for ADA protection.
The question I would ask you is whether this particular restriction prevents you from doing an "essential" function of your job. For example, if you have a five pound lifting restriction and your job regularly required yu to lift 40 pounds for the majority of the work day, then you have a restriction that may prevent you from performing an "essential" function of your job. It then boils down to whether there is something the employer can do so that you can perform this work. The law is not going to require the employer to buy you an expensive device to lift stuff. Nor is it going to require the employer to assign someone else to do this work or to give you a vastly different job than the one for which you were originally hired to do.
On the other hand, if you have a similiar restriction but you spend the majority of your work day in a cubicle on the phone or in front of a computer, but once a shift, you have to lift a forty pound box, that particular task may not be "an essential function" of the job. The employer shoud be able to modify your job to remove this particular task without any adverse business impact. BTW, smaller employers are exempt from many of these requirements. It seems like you do work for a larger one. Nevertheless, I want to menton employer size in case my assumption about the size of your employer is wrong.
I will be the first to tell you that most of these cases are not quite as "black and white" as the above examples suggest. I suggest that you decide whether this particular restriction is indeed "a deal breaker" in terms doing the job tht you were doing. In other words, how often do you perform job related tasks that would violate the restriction as it presently exists? If the answer is only occasionally, perhaps there is relatively easy way to accommodate it or, after discussion with your doctor, he or she may feel that it would not be inherently risky for you to perform the task in question on an occasional basis. If the answer is regularly, then you really need to think about whether there is something simple (and inexpensive) that your employer could do that would still allow you to do your job. Alternatively, you discuss with your physician what the health risks to you might be if you did ask him or her to remove the restriction, assuming that your doctor might be willing to do so.
There is no easy answer here. You may have to consider going into a new line of work. That may mean retraining and/or looking for a different kind of job with a different employer.