Avaya have dropped the price on whatever they now call what was the 3050 SSL VPN. You don't need to order it in 50 connection blocks anymore - just 10 session blocks. Its all virtualised too, so hardware required.
I used it for testing a bit about a year back and found it pretty good. You can have an 'always on' connection from your customer to your VPN (consumes a license the entire time), or just have the customer dial a shortcode on their system when you need to do any remote work for them (consumes a license whilst connected).