Personal TLDR research.
Western supply chain bottlenecks like $LPTH and $AXTI:
$MTRN - Beryllium (Spor Mountain)
$HALEU - Uranium | SMRs
$ESE - Space fuel tanks (through Vacco)
$GHM - Vacuum Ejectors & Surface Condensers | U.S. Navy
$FEIM - Atomic Clocks
$OPXS - Light Laser Periscopes
$TAYD - Vibration
$PKE - Heat
$VNP.TO - Western gallium
$TDY - Rad-Hard Image Sensors $RDW - Roll-Out Solar Arrays
$PDFS - Exensio Yield for Intel 18A
$WOLF - Silicon Carbide
$RELL - Ultracapacitors & Magnetrons
$CPSH - Thermal / Aluminum Silicon Carbide
$VREX - X-Ray Tubes
$GSM - Western Silicon Metal
$INTT - Extreme Thermal Cycling
$CODA - Turbidity (Murkiness)
$NTI - Corrosion $PLAB - Photomask
$MKSI - Plasma Control
$KULR - Explosive Heat
$PESI - Radioactive mixed waste.
$CVV - Gas-to-Solid Deposition.
$LPKFF - Laser Induced Deep Etching/ Glass Substrates
These are just more of the "under the radar" small caps I was researching -> ended up choosing $AXTI and $LPTH if people were interested.
Lot of them have terrible fundamentals despite being vital eg: $IQE (already pretty known), so it's not a good idea to just blindly buy a bottleneck.
There were a lot more out there I haven't finished researching (so didn't include), and it's a lot harder to pinpoint ones that haven't been priced in.
But wouldn't be surprised if a lot of these went up 5x over the next year.