I would think most domain registrars would allow that...

I personally use Godaddy and Namecheap but i'm leaning towards the latter...

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I don't recommend you shrink your site name by use of a proxy. Those short tinyurl are looking tacky. The easiest thing to do is buy a new dot com that is short and relevant to your site and forward it to your old site while also masking the old named site with your new one. It is all quite simple and can be done at time of your site purchase within domain management at your server.

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