There does exist a 4G version of the cross border SIM cards. Ordered this a few weeks ago and got it this week: https://www.amazon.com/China-Unicom-...dp/B01LXBV2WE/

Unlike the other cross border SIM cards though, this one apparently only has a HK number. Instead of free incoming calls, incoming calls cost HK$0.45/min; the tradeoff is that unlike the Cross Border King Dual Extra, which has a HK$18/month fee, this one only has fees of HK$6/month.

It's good as long as activated before the end of next year and I'm almost certain to go back to China before then.