There are always posts suggesting the use of a VFD to get 3 phase, but your best, and cheapest route is to simply build yourself a rotary converter. All you need is a 3 phase motor with about 1.5 to 2 tmes the HP of the motor your wanting to power, a handfull of capacitors, and a couple of electrical contactors/motor starters.
That being said, if youcan find a company that works on commercial wells and sewer plants, etc they will typically have pump control units, etc that have been replaced that have both the capacitors and the motor controlers needed in them. In my case my dad works for such a place and I was able to get the items free, but most places consider that stuff scrap so you ought to be able to get everything cheap anyway. Along the same lines find a local scrap yard that takes in commercial electrical stuff. The contactors are the most expensive parts, if you had to buy them new, so i you can find an old commercial machine with a few of them in the control panel, again you can usually get them relatively cheap from those kinds of places too. As far as the capacitors go they are relatively cheap, especially if you check with somehwere like Surplic Center for the oil filled ones.
Before you do anythin though do some looking online and you should easily find quite a few sites that give you all the information you will need to figure out what parts to buy and how to put them all together into a working rotary converter. I built one last year for my milling machine using a brand new, bought off CL for $200, 10 HP motor and the components from two of three old well pump control boxes that had been changed out after lightening fried components I had no use for. Got it wet up so all I do is push a button to turn it all on, and then push another to turn it all off. Easy as pie and it works great.
Good luck and post again if you need any more help.