Is there a sample 4187 or otherwise, requesting waiver for travel for tdy?

You may need an ETP if those movement policies are still in place. Your S1 would be the best place to start.

S1 here,
It depends on what the TDY is for. If it is for a PME, then the latest from HQDA is that there is no longer an ETP required for travel. There are a few other criteria for what constitutes a need for an ETP and the guidelines are constantly changing.

My recommendation is to confer with your unit's S1/schools NCO and confirm whether your TDY requires an ETP or not. Bottom line though is that if you have an ETP approved by the first GO in your chain of command, you will be good to travel regardless of when the ETP was signed.