Repair /rebuild question

I was rummaging through my closet and discovered an air pistol that I have owned since childhood.It is a .22 caliber CO2 single shot.It appears to be made by Crosman but sold by Sears Roebuck as a Ted Williams signature model.It is inscribed as a Match Pistol model 126.1909.It has a 3 position power setting and I do remember that this packed quite a punch back in the day.I loaded a CO2 cylinder to shoot it but I could hear air leaking.Any suggestions on how or where to get replacement seals for this pistol?
 
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