A tailored dress shirt is your best option, but any shirt that fits your shoulders correctly will work as long as that shirt has sleeves.  The accuracy of this measurement depends entirely on the shirt you choose to measure, so make sure you pick a good one. For the sake of accuracy, use a shirt that fits in the shoulder area as correctly as possible. If you want a looser fit, you can always add 1 inch (2.5 cm) or so to the measurement after you take it. This measurement can be substituted for your back or standard shoulder width measurement. Do not use it to substitute for your front shoulder width measurement, though. Since this measurement is not quite as accurate as one measured across your actual shoulders, you should only use this option if you are unable to use the traditional method of measurement. Place the shirt on a table or other flat working surface. Smooth it out so that the material lies as flat as possible. For the sake of consistency, you may want to keep the back facing up as you measure. This does not matter much, though, since the location of the shoulder seams will almost always be the same on both the front and back of you shirt. This measurement is your shoulder width. Consider marking it down and saving it in your records.  While not quite as accurate as a shoulder width measurement taken from your actual shoulders, this measurement will almost always provide a close enough approximation to your true shoulder width. This measurement is most commonly used for tailored men's pieces, but it can be used for both men's and women's tops.

TL;DR in Indonesian:
Temukan kemeja yang pas di badan Anda. Bentangkan pakaian. Tuliskan hasilnya.