Hi @Eli !
Thank you for your question! I did a quick stock check on the items that you inquired about and it does look like your best bet is to purchase them online, as @REI-LizH suggested, as inventory for both items is quite low. I'd also echo what she mentioned and suggest that if you do decide to purchase both harnesses, you can compare and contrast them at home, with your gear, as well as in your local store with advice from an REI employee. When you decide on a harness, you can return the other that did not work for you.
Here's a link to the C.A.M.P. USA harness
Here's a link to the Petzl Hirundos Harness
I hope this was helpful to you!