With that price you're basically stuck with cheap chinese options. It probably won't matter much which you buy, they will all likely be similar quality. I've bought from four different companies, Meierlight, Spacelas, Laserking and EMMA Light and they were all comparable. Perhaps the most important factor is whether the company you buy from are respectable with good customer service because it's likely that you will need it, because the cheap parts often lead to something breaking. That happened with the green module in two of my projectors after just a few hours of operation. However luckily both the manufacturers were honest enough to send a replacement.
If you step up the price a little bit there's the Laserdock at $700. It has a dac integrated so you save a bit of money there, and the projector is relatively good quality. Noiseless too which is great for hobby use. I have one of those also and I like it. Downside is no ilda input so you have to use the integrated dac.
http://www.wickedlasers.com/laserdock
Otherwise there's this, which seems to be manufactured by the same people as manufactures the Laserdock and with similar specs, except ILDA input instead of integrated DAC, and cheaper. It has 520nm direct green which is more reliable and gives better modulation performance than DPSS green. The analog modulation is optional so make sure to specify that. You don't say whether or not the $500 limit includes a DAC or not but paired with for example one of my Helios DACs it will just barely be below $500 excluding shipping. But I haven't tried this one personally so I don't know whether it's actually as good as the laserdock or not.
http://www.magnumlighting.com/English/Products/2016/0531/104.html