With 90+ eSIM brands and over 140,000 data plans, eSIMDB is the world's largest travel eSIM comparison site.
bargain for travel: https://gigago.com/esim/europe-uk/
See also: https://www.simonlyfinder.co.uk/esim-only-deals
Boost data only
Unreal roam in Canada and Mexico only
H2O pay for usage
Ultra is only $.02/MB for data; voice/text cost less with H2O
US Mobile "Global Pass", data only; do unlimited US plans do voice/text when abroad?
https://thesavvybackpacker.com/best-uk-esim/
a few under $30 from SIMoptions
data-only: https://cybernews.com/best-esim-providers/best-esim-for-europe/
Three UK: PAYG + data pack £10, eSIM requires contacting a human
https://www.three.co.uk/support/sim-support/esim
Lyca Mobile: £10/20GB, unlimited UK voice/text!
https://www.lycamobile.co.uk/en/bundles/sim-only-deals/#best-value
Physical SIM only:
Orange: €20/12GB, 30min/200SMS
https://travel.orange.com/en/buy-a-sim/offers/united-kingdom
Vodafone: €23/10GB
https://travel.vodafone.com
Wikipedia | list of US MVNOs
https://www.whistleout.com/CellPhones/Guides/Best-cell-phone-plans
Red Pocket $20/5GB, all 3 networks available including locked phones, unlimited slow data
Tello: a la carte; $16/10GB w/hotspot & 100 min! Hard limit, one-time data packs available
H2O (ATT): $18/3GB (2GB hotspot), unlimited slow
PureTalk (ATT): $20/3GB (2GB hotspot)
Ultra (T-Mobile)
US Mobile $10/2GB light plan, $20/10GB, unlimited 2G data; 20% off for paying annually; also "Unlimited Flex" plan (annual only) with 5GB hotspot
Twigby (Verizon): $15/2GB
FreedomPop: $10/1GB, no more free plan
TextNow: free talk/text, various data "passes" available per hour/day/month; requires smartphone and app, with full Google Play Services and account
Hello Mobile: $10/1GB, $23/unlimited paid quarterly; hotspot only on $40 plan
Lyca Mobile (T-Mobile): $19/3GB, less during intro promo; probably no hotspot
AirVoice: $18/3GB w/o hotspot paid monthly, $14/2GB hotspot paid quarterly; promo pricing is confusing, hotspot plan might jump in price to renew
Ting: $20/2GB
Boost: $15/5GB, data shuts off after allotment
Boost Infinite is post-paid, but $25/month for unlimited BYOD; hotspot is another $10
Unreal: $15/5GB (1GB hotspot), unlimited slow
Naked Mobile: $35/10GB w/voice, $30/20GB data only
Also, Talkmobile is very competitive, on the Vodafone network. They allow tethering (hotspot). Uses a physical SIM, not sure if they ship to the US.
A versatile bike rack option, but maybe we'd just want the tray on the teardrop tongue instead.