So welcome to the modding community If you are new I can link you to a few threads that will help you get started
You could always look on eBay for a PS3 on 3.55 Official Firmware (OFW for short).
You need to search for a 3.55OFW console as its against eBay's terms and agreements to sell the console jailbroken.
Personally I recommend Reaper as he is reliable and has a lot of experience with dealing with console's
But While on eBay you could buy one in terrible condition :/
I hope this helps If you need any help feel free to ask me of any of the Se7ensins staff