I'll DM you the carriers who do it.

@Troy Patt most personal lines insurance carriers can not do an Umbrella without going over your Auto policy as well. 

@Brad Peralta You should be able to obtain an Umbrella policy regardless of which carrier the underlying policies are with.

@Ryan Carriere is a CPA specializing in Real Estate investors and an investor himself

Hire an Insurance broker that can shop the many options without being bias to any one carrier.

I can't combine under one carrier because the standard carriers all declined the Portland properties so we had to go with a non-standard carrier.

My current carrier, State Farm, gave me a quote but agent also said they are probably not best carrier for this type of unit. 

Hello BP,Aside from top rated insurance carrier what are the most Important things to consider in a policy for an Apartment?

But his is a cash business not dragged out waiting for Medical Ins carrier reimbursements indicative of a private practice.

Even if you're highly confident about a property you've personally walked through, at least obtain a basic 4 point inspection that at least inspects the items insurance carriers are typically concerned with: Electrical, plumbing, HVAC, Roof, hot water heater.PS in all likelihood you'll have a much better buying experience your next go around.