For the type of sound your looking for might be best to do one of the suggested, or instead of purchasing a pack get a physical modeling synth/vst:
-for most plastic sounds I prefer to use a shotgun mic and just go record random things: a spork running it along a fence, use said spork and drop it late night in a tunnel.
Plastic bottle,.open and close it. Plastic bottle take lid, tap or bang it on the opening, or slightly squeeze it and tap while opening closing for a sorta durbka (sp?) drum sound…
Get out old Tupperware, get in car…run it over…drop said Tupperware…throw Tupperware at wall…bang lids together…
With this method…you just do stuff to plastic, record it, take it into tape machine, d.a.w. whatev… then make snippets of it… sometimes you post process it, sometimes you layer it with a synth white noise or just save some noise from the recording and layer it
Method 2:
Use a synth adsr: 0 at 0 Dec (to start) 0 sus 2ms release… dial decay and rel til you are pleased… record sound…process sound with a delay that has 0 feedback…1ms time
Feed this into a multiband compressor, feed that into a soft clipper, into a series of all pass filters, saturate maybe like more distortion, dial stuff back to get most of the original sound to be present and not dominated by FX, compress glue, limit
Method 3:
Determine what texture of plastic do you want… playing card on bike tire spikes, plastic keyboard keys being tapped, rapid lever being spun?
Layer this with a bit of noise, a synth or other sound…
Add it to Synplant2…have it create multiple sounds…record those .
Edit them with short transient shapers (- sustain positive attack), use an envelope shaper and make it sound short snappy…
Final tip I’ll offer:
Use a no input device like Sherman2, record random generated sounds, edit them on a sampler, resample in other hardware,.feed it to your machine of choice,.then design it with similar ideas described…
World’s your oyster…just gotta decide which tool you wanna use to shuckit