Tim:
A new piston spring is available directly from Crosman, Part #C1K77-010, fits all C1K77 series (Quest1000, Storm, Sierra Pro, Remmington Summit models) priced at $5.70 each and only a 585-657-6161 phone call away. The synthetic piston seal Part# C1K77-002 priced at $3.60 ea. and breech seal Part#C1K77-008 priced at $1.00 are also available. Their flat shipping rate of $4.00, regardless of order size is, VERY reasonable. (They can resume sending me my quarterly commission check any time now - hehe)
Parts Manuals and Parts lists with exploded view diagrams in pdf form can also be found for much of what they sell, if you follow the appropriate links at Crosman.com
Perhaps this info will help.