Former Pentagon research chief Dr. William J. Perry is being sounded out as a possible replacement for his ex-boss, former secretary of defense Harold Brown, on a special presidential commission studying the future of the controversial MX missile, informed sources said.

Sources close to the commission say they think that Perry would restore to the panel some of the technical strength and political influence they say they believe was lost when Brown resigned unexpectedly last week.

Perry, a senior vice president of Hambrecht and Quist, a San Francisco investment banking firm, served under Brown in the Carter administration as undersecretary for research and engineering, the Pentagon's third highest ranking post. He also served briefly as a consultant to the Reagan administration.

On Jan. 3, President Reagan appointed an 11-member bipartisan commission on the MX to suggest ways out of a deadlock with Congress, which has declined to authorize production money for the missile until the administration comes up with an acceptable way to base it and keep it safe from attack.

The MX figures prominently in the administration's defense and arms control plans, and the White House hopes the new commission will reaffirm the need for the missile and that the panel's blue-ribbon makeup will help convince Congress.

Brown, a nuclear physicist, was viewed as especially important because his technical skills are respected in Congress and because, if he supports MX, he might help persuade Democratic opponents.

Brown resigned last week to avoid any conflict of interest because of a consulting arrangement he has with a California-based firm with MX contracts. The waiver procedure that could have allowed Brown to stay on the commission was, in the view of sources close to the panel, badly handled by the administration and not acceptable to Brown.

He has, however, agreed to serve as a consultant to the commission, and White House officials say they believe he will still be influential.

Nevertheless, there is a move on to find a replacement, and sources said Perry has been sounded out by the commission chairman, Brent Scowcroft.

The panel is scheduled to report to Reagan by Feb. 18.

Perry, like Brown, has been a supporter of MX, but both have been critical of the Reagan deployment plan, known as Dense Pack, which would bunch the missiles closely together. Congress rejected the Dense Pack basing mode.

Brown and Perry were architects of the Carter "shell-game" plan for the MX, which involved hiding and continuously moving 200 missiles among 4,600 shelters.

Some combination of the Reagan and Carter ideas is one possibility that the commission might recommend. If that occurs, the association of both Brown and Perry with the commission could be important.