Edup makes some 3G routers, that may work for your needs. This one supports HSPA+, and operates from a SIM card:
http://edupwireless.com/product-5-1-mini-3g-wireless-router-en/137282
(For anyone else, also see these models...)
http://www.buyincoins.com/item/8260.html
http://edupwireless.com/product-5-3-wireless-broadband-router-en/137284
It seems to be what you want, although I have not used one in person, and thus I can't say if it will do the job for you, or if it's rubbish. No data sheet either, but I don't expect any for consumer devices.
Another solution that may work, if your mobile has unlimited data, is to run a third-party WiFi programme on your mobile, and use a DD-WRT router in
wireless repeater mode.
If you enable root access on an Android device, you can install Linux tool, and use a third-party programme such as Barnacle to create a wireless network that doesn't utilise the built-in 'tether mode', and thus bypasses caps.
The main drawback of options such as this, is that the connection of any 'hotspot' device tends to have problems when you add multiple clients to it. I have used my mobile in this way when needed--when I am off-site, or travelling--and had mixed results, but it does work.
One thing that I noticed is that (on my older Android device), some systems would intermittently drop their connection. I started a ping loop on each, and that generally rectified the problem, acting to keep the connection alive. The problem was most notable on the W7 netbook that one of my associates was using, and he had to continually reconnect, or reboot, due to horrible drivers on his system.
I have a Broadcom chipset on my netbooks, and that generally was more viable, although I still needed to keep it alive. It may have been due to some problem on the mobile itself, as it was a rather unreliable device, and I gave it a great deal of wear and tear. Even so, it was better than paying for a mobile hotspot disc that had bandwidth caps.
Aside from this, you will want to use browser spoofing, to avoid browser-based detection by your mobile provider. (Any client-side software that announces itself by name over a port is suspect to discovery.)
Any other option will cost you, both for a data plan, and for equipment. There used to be a decent variety of mobile modems, but the carriers have all shifted to a hotspot service contract, and flog their own equipment as part of those data plans, dissipating true, standalone mobile modems.
I used to use one of those PCMCIA mobile modems, and I haven't seen any for sale in ages: I occasionally run into a WWAN card for something, but they are rather rare now. Even with the hardware, you would still need a plan that Most of what I see are those horrid little USB modems, and you already know what to expect of them.
