I would recommend them highly. You have a problem that is two fold. Chances are you don't qualify for disability insurance if you work part time. I don't know of a company that makes it available unless you work more than thirty hours per week. Being self-employed makes it even more difficult to get.
Disability insurance is, under the best of circumstances, expensive to buy on an individual basis.
The reason is that statistics show that almost everyone will suffer a disabling injury of some type before they're 65 years old. In addition, in years past, companies underpriced and over-extended benefits to very high earning occupations that have ended up costing the companies dearly. A couple of years ago, many companies got out of the individual disability field completely. If you would like to find out if you can even qualify for a policy, contact an agent who is a broker or look for a brokerage firm that carries more than one company. They should be able to give you more than one quote.