I do mind having that code be closed source and not available to me as the customer who funded its initial development.

I guess that depends on what level the funding was. If the employer wants to get something on the cheap by hiring a part time consultant and avoiding paying benefits, I'd have no problems with the consultant hanging on to their rights. There is also a difference between one-time use and permanent use e.g. the difference between a temporary sign and a logo. If the employer pays the rate for a temporary sign and then expects to get the logo, I have no problems with the designer keeping the logo rights. If the employer pays for the logo at a fair rate then the consultant doesn't have much argument for retaining those rights.