Depending on how picky you are, check out ebay. Bayonets range from 20-100+$ I'm kind of picky. I wanted to stick to all colt parts only. I paid about 100$ canadian after shipping and conversion for mine.. I had bought 2 of them, sold one..
This one is colt but "made in germany"
with a "U.S m8a1 scabbard"
Some colt lovers will pay up to 200+ for a colt bayonet, Ive seen it happen! But, If you dont care you can get one for cheap
There were many companies contracted to make the m7/m9 ,
so check out this website;
http://armscollectors.com/whbayo.htm
here's mine;
Don't let people rip you off.. those other bayonets go for 15-25$ + 10$ shipping on ebay, so don't pay over 50/60$ canadian in the EE or else you get ripped.
Just to get an idea go to
www.ebay.com and type in "m7 bayonet"
Also, watch out for the type of flash suppressor you have on your AR.. most will fit, some will not..
for example..
mine wont fit on this:
But it will fit on this
and this
hope that helps, Im no expert, this is just from my experience and research
good luck.
===== the m4 you pasted is for the m1 -- like I said, check out that website I pasted, it will tell you what bayonet you can use.... m7/m9 + brands =====