Sure ! 24 gifts to your friend ;-p
Maybe you can stick a simple slinky toy under cause it's impossible to find in slinky.
This item was the cheapest, I found some with 50$ shipping to Europe
I don't think you will ever find a slinky that costs $15 or less including shipping fee, but check this out https://www.etsy.com/listing/704212700/vintage-glow-in-the-dark-pvc-alien
It's $19 excluding shipping fee
This may not be very similar, but at least it gets the slinky part, I'll keep searching tho
https://www.ebay.com/itm/Brand-NEW-Boingzz-Orb-Odditeez-Bendzz-Expandzz-SLINKY-Green-Alien/124306207392?_trkparms=ispr%3D1&hash=item1cf13a32a0:g:QxkAAOSwNYFfPoV4&amdata=enc%3AAQAFAAACYBaobrjLl8XobRIiIML1V4Imu%252Fn%252BzU5L90Z278x5ickkp2NA0WuhQytmt4dbStg00MYBeUoFmr5XD9ArVsPbsENf6NEPYJN%252FEGrZhtfgu3ye%252FmrdSoUvReSjVDe8TKJEs90HI5bu7X0YeFAEz5NZfJCn2QdRCwaVWL2Zc9pUs5qhzUt3GXpiwNPR%252BtyrS%252Bfwx0dzpd%252BclfPQwRgtLcp12L7qG6ai5K1z02wJ9M18WvJZQZciKnGpYMfo%252FUdp%252BlniG4Xp%252FiO2JS8kO5Dkz3Agt3GFMew7DAD%252F7soR%252FI%252BStgWca%252F5662GNeIVrLlqOntSx78jwhEW8MzL%252F59Sr%252FzYPMbmt7EF19VdJLQzRcmhdP0%252FkaqWGAKn6QCPqNZBol3RNZ7TUtbzYqeLV05FrOFSiFSqhpz6VVYU0uS9LK58CC8n2WAW3U3zG8X%252Bwoq5SJkk2cT3DaMBurXSIfeg3OPCttVyBrBqaTtT6yFROjEAXelzfR%252B1ynwBmWSd7mBb6gm%252Fn3ugmytYMBh91hSVH79I%252FNy1yVEy9kXvq94iRDTIZ47pKrpT6MiBqQK0zg%252BlC2%252BdLvPSeyjtpG9Q89yAcL5igt%252FUgmuldSJFuLIl6%252Fh%252BXWkFkx%252Bjg7x762GTHNzBf0w8eDD5CXgJleCqZCIYEbSxlniNe8TjSgGe8apVuBluRjMdR%252FOjXk7H4SFLPzbtKzypsDNVkMSFQbry9OlAFhzi86tdkkbERYKJYbayRNPsGoObAnU7BWTZ1cpBiZ%252BDzNB81pODKhCj%252FHw8wnnkiE%252FTaaycJOOdyLUzcgYGdMPY5qpux%7Ccksum%3A12430620739284fa2421313041059c30d3a11d70beb7%7Campid%3APL_CLK%7Cclp%3A2334524
here is an alien themed glow-in-the-dark Slinky keychain
https://www.google.com/shopping/product/10122108010146978150/image?q=alien+theme+glow+in+dark+slinky&client=ms-android-americamovil-us-revc&prmd=sivn&sxsrf=ALeKk01NrggvLJwYV2bViKQ2TZ7_QwxBQg:1604874190353&biw=360&bih=592&sa=X&ved=0ahUKEwic_Mai_vPsAhVNWs0KHc4aC0gQnUAIwAU&prds=cid%3A10122108010146978150%2Ccs%3A1%2Csgro%3Aiv%2Cmvi%3A0
its on etsy for almost 20 dollars and its not that epensive if u really wanna impress your friend here the link
https://www.etsy.com/listing/704212700/vintage-glow-in-the-dark-pvc-alien