Like all firearms, it depends on conditiion, and to some extent location. I just bought one for $50 in poor shape, they can fetch $150+ in excellent condition.
Left side under the rear site. That's where it is on my 99M1.
The 99m1 was built from 1964-78. It was built to resemble the original M1 Carbine, as used in WWII. The 99M1 is the same gun as the Marlin 989 or 99C, so parts interchange with them. Answer The 989M2 is the clip-style magazine, as opposed to the tube style found on the M1 :)
Try Numrich, I'm from New Zealand & they've even sent me some parts for my 99m1 before! This is their link. http://www.e-gunparts.com/
The Marlin 989M2 .22 caliber semiautomatic rifle was made from 1965-78. It was originally sold with a seven round box magazine (what some people call a clip) but the modern (written in 2012) Marlin brand 10 round or 7 round nickel magazines work fine in the 989M2. As extra information be aware that a "twin" of the 989M2 was made with a tubular magazine, holding nine rounds, and that twin is the 99M1 made from 1964-78. These two Marlin rifles are nicely made models with walnut stocks and handguards. They were made to look like the M-1 Carbine military rifle.
Plug the phrase "Marlin Model 99M1" into Google, and you'll find a wealth of data and sites relating to this firearm.
Good luck. Every site on the Internet seems to be out of the 10 1/2 inch magazine tube for the Glenfield/Marlin 75. Keep in mind, the Marlin 99M1 uses the same tube, but that is just as hard to find. I have been reading up on converting it over to a Marlin 60CC Magazine Tube inner and outter, but not even sure that will work.
Brand new about $195.00. * They have been made since 1960 and I recently bought a used one for $60.00, in excellent condition. Depends on the letter/letters following the Model #... 99 99C 99DL 99E 99M1 etc..
$100-$150 I very much appreciate you adding "Please" to your question. I wish more people would do that on Wiki. USDF