"Is this some kind of joke?" outspoken Russian journalist Oleg Kashin asked while others suggested it was a PR stunt to sell more furniture.
The cot's makers said they had sold "around 10" of the items, but argued the design was "nothing unusual".
All 298 people aboard Malaysia Airlines flight MH17 died in the attack.
International prosecutors say the missile was brought into Ukraine from Russia and launched from a field in territory controlled by Russian-backed rebels, who were fighting Ukrainian government forces at the time.
Russia says it cannot accept the findings as the final truth.
The Buk cot is produced by a family firm, CARoBUS, in the Russian city of St Petersburg and is part of a special series that also features a tank and a plane.
Normally, the firm makes cots shaped like cars, ships and planes.
"I see nothing unusual in a cot like this," CARoBUS director Anton Koppel told local news website Fontanka (in Russian).
"Some grow up to be doctors, others bakers and some soldiers."
Apart from Kashin, comments by users of leading Russian news site Lenta (in Russian) include the following:
"Free PR, market demand - the guy's a genius," wrote another user to which someone replied, "Calling him a genius may be going too far."
A Russian children's cot in the form of a Buk missile launcher - the weapon that downed a plane over east Ukraine in 2014 - has raised eyebrows.