Scotlandaccordions specialise in and manufacture accordion MIDI sound systems and also manufacture accordion microphone systems.  We have searched for a really good sound system which suits the accordion but does not break the bank.  
This model meets our criteria:

Single piece unit including mixer amplifier with just the right number of connections for most accordion uses.
Powerful built in speaker for home or stage use.
Durable and portable with possibility to use as public address speaker / stage monitor / Stand mounted option (stands cost extra).
Really good sound and price.
Specifications
ACTIVE PUBLIC ADDRESS SPEAKER HOUSED IN STRONG ABS CABINET FITTED WITH A HIGH QUALITY MIXER AMPLIFIER.
System especially suitable for accordion use.
Can be used as a stand alone system.
Ideal for mobile use.
Power 400 Watt Maximum.
220-250 volts 50-60 Herz.
10 inch woofer.
INPUTS 1 microphone inputs, RCA, Left and Right.
Frequency response 45 Herz to 20 KHz.
Dimensions 530 x 280 x 330 mm.
Weight 9.3 KG.
10 inch speaker cone.
Titanium compression horn driver.
Shock resistant ABS cabinet.
PTC driver protection.
Microphone / line inputs with volume controls.
35 mm top hat fitting.
Supplied, Recommended and guaranteed by Scotlandaccordions as suitable for any accordion which we supply it with.
Note do not buy a speaker system for an accordion without a horn and bass driver.  Cheap guitar amplifiers are designed to reproduce low note string sounds and do not usually incorporate a horn or treble driver.  You will thus not get the frequency range of the accordion amplified properly.  Please come to Scotlandaccordions in order to get a suitable accordion system amplification kit.