BR 200 - NAT Loopback

I am needing NAT Loopback functionality on my BR 200 Router. I understand that this feature wasn't enable on the last 2 firmware releases, so my question(s) is this: 

1) Where can I get a previous firmware release that does have NAT Loopback enabled? I can only seem to find the last 2 releases. OR

2) Can someone walk me through or provide me a link to a step by step to enable one of the suggested workarounds? I am not a Network proficient, so I do need a little hand-holding I'm afraid. OR

3) I have a secondary router (Linksys MR9000) that does have NAT Loopback, however, it does not have Open VPN capabilities, which the BR 200 does. Does anyone know a way to utilize the MR 9000 for NAT Loopback, while using the BR 200 for Open VPN? OR

4) If all those options sound impossible, what would be a good Business Router that has NAT Loopback and Open VPN capabilities? We are a small office (5-10 connections, 3000 sq. ft.)?

Thanks in advance!