I need a physical address in Belgium to start an SPRL.

I will not use my residential (hotel) address because I move around too much.

The common practice is to use the accountants address. I am opposed to that partly because I do not want to add any complexities to being able to change accountants.

A "virtual office" seems to almost be the right answer. However, the virtual offices I have found so far bundle lots of telecom and other services that I don't need - making the cost upwards of €90+/month.

I just need a mailing address (and I don't think it's legal to register a company to a post box). Suggestions?