You're going to have to download the stock MK4 rom and extract it with a zip file manager. you will need to make sure you download either the odexed or deodexed version of the rom in order to extract the correct apk you're looking for.
Edit: since you already have the rom zip on you pc, why don't you just extract the apk you are looking for with WinZip, 7zip or similar zip file program? That way there's no need to download anything. Another option might be to download the MX video player from Gogle Play. It's probably the best but I also like the stock Samsung video player. Looks like somebody come through with the apk you're looking for. So how come you don't have the stock video player in the first place?