Have a look at :
Diode-pumped solid-state laser - Wikipedia, the free encyclopedia
Speedy and Hwang21 are 100% correct. There are real and valid reasons no manufacturer producing large numbers of units offers a bare 532nm module with an output greater than 800mw to possibly build into a handheld laser.
Making a DPSS laser is a complicated , expensive, & delicate/tricky process without room for error to get a stable and excellent result. It is not well suited to hobby people making one--way too expensive for that. Is not simply buy a diode and put it in a host with a power source as a 445nm is. Is not practical cost and time wise to make one. Would be many times the cost to buy a green module and put it in a host.
Just an 800mw 532nm module alone from lasever last time I looked was $570 and that would need to be put into a host and provided with a power source etc to make it into a handheld laser.
You don't mention what you want to do with it or how longer you want to be able to leave it on or what your budget is.
Keep in mind 2X brighter requires 4X the output power. So a 1000mw 532 is about twice as bright as 250mw. The cheaper you go the shorter the duty cycle "on" time due to heat.
JetLasers PL-E Pro are highest quality, highest output power with longest "on" time at a very reasonable price considering what it would cost you to do something like it yourself.
The 500mw from laserer you mention is a toy you can only be run for 1 or 2 minutes at a time without damaging it and not IR filtered etc.
A PL-E Pro 500mw is a professional quality unit that you can run "on" for a very long time and is IR filtered for example---well worth the few dollars more.
If you want 1W or above you need to go with a lab type fixed place of operation unit.
Your best bet at a rational price is as Speedy says, " I recommend the PL-E 800 as well. Max outputs are usually over 1W. If you need CW over 1W I would recommend a lab style unit. To much heat to dissipate in a portable. " His peaks at 1139mw! Nice!