One-Time Addon

Is there any way I can add a one-time addon while creating a subscription? Currently I only see a way to add a recurring addon. If I have to add the one-time addon seprarately, the customer will get multiple invoices, which is lame.

Example: We are an ISP and when we have a new customer, we need to be able to add a one-time Installtion fee, one-time Activation fee, and sometimes other one-time items as well. Any way I can do it all at once? If not, this should definitely be a feature that gets added. Or at least a way to add multiple, different setup fees?

Thanks!