Here is an idea that is not mine but is very useful...Portable Timpani Tuners for older timpani that either don't have tuners or they don't work. I once used them to play the Bartok 2 Pianos and Percussion so I know that these work. You might want to keep them in your stick case for emergencies.
All you need is :
4 medium binder clips (Office supply)
4 pieces thick thread in 4 foot lengths.(sewing goods)
4 thin pieces of felt 2 long and1 wide
cut into pointers. (sewing goods)
4 fishing sinker weights about 1 1/2 long.(sporting goods)
1 flair felt tipped pen (not permanent ink) (for plastic heads only)
Directions: A) Use each thread to sew along the length of a felt pointer. Sew in and out as shown
about 5 times in a line so that the pointer will slide along the thread but not too easily.
B) Tie one end of the thread to the binder clip and the other end to the fishing weight.
C) Attach the binder clip to the toe of the pedal and position string between two tuning posts
as shown below. Changing the direction of the string will switch the tuning sequence from ascending to descending.