There were several different Walbro carbs used on the 046 over the years. These exact numbers are probably only available from Stihl but to research the sizes, you may find another carb that will work?
HD-24A 17.6 mm venturi
http://wem.walbro.com/walbro/product...&Series=HD
HD-16-318
HD-9A
HD-8-318
HD-11-318
HD-10B