Do you mean based on the meaning or sounding similar?
How about:
Octavia for sound similar to Oscar.
Oscar means spear of the Gods. "Also possibly from the Gaelic phrase "os cara", meaning "friend of the deer"."
So how about Cara.
www.thinkbabynames.com/meaning/1/Oscar
Jasper is a precious stone, it means, treasurer; spotted stone, so I think so Ruby, Sapphire etc.
Or try something different - Almas - Arabic name meaning diamond, Amber - English jewellery and colour name of Arabic derivation, meaning simply amber, Amethyst - English name derived from the name of the precious stone, itself from Greek amethuskein, meaning "not intoxicated; sober," expressing the ancient belief that the stone had the ability to protect one from drunkenness. This name is sometimes given to girls born in February. Beryl - English name derived from the name of the gem, itself from Greek beryllos, a word applied to all green gemstones. Emerald English jewel name borrowed from the name of the precious green gemstone which is the birthstone of May. The name is also a form of Spanish Esmeralda, also meaning emerald. "The emerald was once believed to have the power to protect chastity, ward off evil spirits, cure dysentery, epilepsy, and help poor eyesight.? (See website.)
Or read more at www.names-meanings.net/names/jewel-gem-female
Flynn and Finlay are harder, for sound how about Fiona or Fifi. I like Fifi as an abbreviation for Fiona.
Flynn is of Irish and Gaelic origin, and the meaning of Flynn is "ruddy-complected". From Flann.
www.thinkbabynames.com/meaning/1/Flynn
So I think of Scarlet, or maybe again I think of Ruby, or maybe Rosie,
Finlay means fair warrior, for fair how about:
Alvino (White, Fair Spanish)
Alba (White, white hill, Latin)
Akasma (White climbing rose, it's Turkish)
and you can look for more at:
www.babynology.com/colornames.html
Congratulations and good luck.