Best bet would be Craig's list or Ebay. The problem with deck extensions is once you have it you never want to go without. So most don't sell them separately, I added one to my 188 VX and when you have two on the front casting, it is not only a big addition to the deck size, but a lot safer in my stumpy reservoir when you never know you are going to hit something and get knocked backwards.
I have one made by ranger with the lid and hardware i am wanting to trade for a new graph..It is out of a 92 362v and was in for a short time,i hate it in a dual console.I did enough playing on the floor when i was a baby..
Any way if interested take your measurements and i will mine to see if it fits.
I think it is like 30" by 27"..
only reason for me to hold on to it is for resale of the boat but it is fine and i need a gps/finder worse.
Yeah that was one thing that kind of disappointed me, the brochure showed the deck extension that was a box with a lid. I tried to get that and it was only available in the bigger models. I went with the one for my model just like redranger, only thing is I wish I would have got the one with the hole in the middle for the spare seat. Only cause I am too lazy to keep taking out the extension to 3 man crappie fish