The best way I've found to handle that is while scheduling the final interview. The one that's further along, ask for the in-person to be a week later then they'd proposed. Try to schedule the two in-persons at the two companies within a week of each other.

The other (risky) way to handle it is to say "I understand that you need a timely response because you may have other candidates you need to get back to. If you need a response this week then unfortunately I'll have to withdraw from consideration, as I won't be able to get back to you by then." Of course, you have to really mean it, and you have to be ok with them going ahead and withdrawing the offer.