If I decide to buy an electric cello, should I look for a special one for left handed people, or I will even have to order a custom one?
Short answer: for an electric cello, there is no basic difficulty in playing left-handed apart from the bridge and the nut, if you have already learned the cello left-handed.
Most electric cellos feature a wood bridge, and its arc shape and groves correspond to the fingerboard's shape and string gauges. The main custom thing you will need is the bridge but you might need a custom nut as well (depends on models). Any good luthier can fit you a new left-handed bridge for a reasonable fee. He or she might even like the challenge of doing something unusual. If your electric cello vendor can make it for you on order, its probably a good solution too, because he will know a few things about interaction with the amplification system. Having the right-handed bridge could be helpful if you want to sell it later.
Orchestral string instruments such as violin, viola, cello, double bass are not symmetrical but this fundamental asymmetry is not seen at first glance and is mainly concerned with the acoustic properties of the cello body which are almost irrelevant for an electric cello. I expand on this subject because at least one answer to this question is really misleading.
- When you have a cello in front of you, the traditional setting has the bass side (C-String) on the left and the treble side (A-string) on the right.
Inside the cello, you have a soundpost on the right side blocked between the table and the back, and a so called bass bar (image taken from http://www.nowakviolins.co.uk/) glued on the table. These two devices are essential to enhance the resonance and amplification of the string vibrations by the cello body.
The fingerboard can be asymmetrical (one possibility is the Romberg shape, with a angled cut on the side of the C string) and with a varying scoop. You can have an idea of this shape here. Unfortunately, the Strad magazine is not online at this moment but there are many subtleties about fingerboard shaping that have been explained in its articles.
The bridge usually follows the ending shape of the fingerboard but not always (it is often asymmetrical in violins and violas, for ease of play and compensation of the position of the wrist, palm and fingers around the neck). It is anyway asymmetrical because the strings have different diameters and you have to be careful on the size of the groves they have to lie in. The bridge transversal shape itself is asymmetrical. You cannot simply turn it by 180° with the same results.
The nut (that part of the cello just before the fingerboard where the strings pass just after the pegbox) has groves with size matching the string diameters. A damaged or badly fitting nut can cause parasitic sound on the strings. This is more dramatic on electric cello which are amplified.
Of course the pegbox and the position of the pegs is asymmetrical but the use of a given peg for a given string is more a matter of common sense and convention, not a problem when changing string order for left-hand playing.
So true left-handed cellos are different in many respects, and this is not only a matter of changing the string order. They are rarer than ordinary right-handed cellos but I do not like this terminology, because string playing requires as much ability and coordination from the two hands, and it is not always clear that a left-handed person might benefit in using its right hand for the fingerboard. Anyway this is clearly a problem when playing in orchestra to play with the bow in the left-hand.