Mate, your revenues are higher than many if not most IPOs that I come across.
I'd recommend reading a ton of prospectuses to see which IPOs are using which consultants/lead managers etc. The costs are always listed in the Prospectus, although generally buried way down near page 100. Then, perhaps contact some of the companies who have listed in the last three years, in a way that you're impressed with, for recommendations.
Also, perhaps just contact some of the investors here for their impressions on lead managers and the like. Last, the investment/corporate bankers involved are more than happy to take your $600k or $1m or whatever it ends up being. Let them sell you.
The cost aspect of IPOs is overblown - it's expensive, sure, and some lead managers really take the piss with the amount of equity they take out of a business, but you also get the opportunity to increase the value of the company by far more than the costs... this all comes back to your 'why' for listing.
The good news is that you're profitable, fast-growing and with a very healthy revenue base - this puts you in a much better position to negotiate terms compared to other IPO candidates who are months away from insolvency.
