From the pens mentioned above I use the springs, the sizes are good for front coils and coilovers. But never thought about the other parts. Thanks! The plastic cookie trays and other bakery trays that have ribs can be used for for rolled upholstery, and I cut my headliners from styrofoam plates (only use acrylics to paint and use double side tape to attach). Medical duropore tape can be cut into 2 or 3 mm strips for seat belts/harness and painted any color (looks like real webbing material) and it's adhesive.
Like the wire source from ear buds.