Recommendations for small NetBSD network box

Apologies for cross posting to three pretty generic CPU lists, but I'm
hoping the answer lies with the expertise reading this now :)

I'm looking for a small box to act as a NAT & low traffic VPN device.

Requirements are pretty simple:
- At least two Ethernet interfaces (100base fine)
- Enough RAM to to run NAT (probably pf), and IPSEC or OpenVPN
(fortunately not both) for up to about 50 web (or weblike) clients &
sshd
- Small (sub mini-itx), and cased (looks like a product)
- USB port to plug in a 3G dongle would be nice.

I could obviously easily find something running Linux, but I'd prefer
to have it running NetBSD.

Does anyone have any suggestions?

David