Hi Wim,
No, there is nothing in the regulations that specifically supports an item like this. As you will know, the HJ-Streifendienst did not have any judicial powers and its sphere of influence extended only to Hitler Youth members. I see no support in the regulations for the idea that SRD members could step out into general traffic with little signs like this and stop motorists and in any case, this was not within their remit.
The SRD had a responsibility to ensure the correct conduct of HJ members taking part in large rallies or the transit of large groups but I'm trying to imagine a scenario where a sign like this would have been required/permissible. Would the SRD have needed a sign to stop traffic/personnel during a rally or large tented camp where traffic was very light to non-existent and where they would be instantly recognisable as SRD members anyway? Nah. Also, the SRD regulations repeatedly mention that SRD members should take care to carry out their duties quietly, quickly and with a minimum of fuss in order to avoid any escalations.
Signs like the one in post #1 just don't make sense and in terms of the regulations there is no reason to believe that they are modern copies of a sign that existed during the period.