Via a search on the Wellcome Trust Library and then google books and the internet archive, I discovered a quite detailed book called "The Flea" by Harold Russell.
As well as a detailed record of the internal workings of the flea, in the chapter on Human Fleas there is a section on performing fleas. There are a items of particular interest to would be performers. The first is that the author suggests that the fleas are harnessed with silk threads not wire, the use of blotting paper so that their feet do not slip when pulling carriages and the rotating pill box for breaking the fleas jumping habits.
Performing fleas are first of all securely fastened, and this is nine-tenths of the secret, and the art of education. A very fine silk fibre is put round the body and knotted on the back. The flea may then be cemented to some movable or immoveable object. It may pull a coach by being attached to a pole made of a bristle. A little paper object stuck on its back is tamed by courtesy an equestrian or a ball-dress. The lively imagination of the spectators is of greet he1p. The strength of a flea is wonderful, and on being placed on a sheet of blotting-paper, so that the hooks of the feet get a bold, the coach travels at a fine pace. In the intervals of the performance the coach is turned over, and the performer with its feet in the air does not get exhausted with needless struggles. Or else the fleas are fixed head uppermost, with their legs extended horizontally, to an upright wire driven into the table. Ladies have fans of tissue paper gummed to their limbs. Gentlemen are in the same way supplied with swords made out of fine segments of wire. When two swordsmen are placed opposite each other and the table is knocked they move their limbs. The swords then clash by chance, and we have a representation of a duel not much worse than may be seen in provincial or even London melodrama.
More wonderful are dancing fleas, for there we have, a real representation of a ball-room filled with waltzers. The orchestra of fleas, all securely flied with cement, is placed above a little musical-box. The music proceeds from the box, but the vibrations make the fleas gesticulate violently over their musical instruments. The dancers spin round on the ballroom floor. The couples are fastened by a rigid bar opposite each other, so that they cannot touch or part. Each is pointed in an opposite direction, and tries to run away. A rotary motion ensues which, to the spectators if not to the fleas, is very like waltzing
Ref: The Flea - Harold Russell - 1913