You have two basic choices - either option should work OK for you.
(1) You can find many online sources for 'generic' AC adapters that should work fine. An example:AC Adapter For ACER Aspire One 532h $11.56
(always check shipping charges too)
You should be able to tell this isn't an actual ACER Aspire One 532h adapter. Hint: Brand New Replacement Product, works as genuine parts, 100% OEM Compatible!!
What's most important are the electrical specs: Output: DC19V 1.58A and Power: 30W Max. This should be an exact match to what's on the Acer part you
(2) The genuine article: ADAPTER KIT 40W WITH AC CLIP/PLUG US $19.56
You can already see that option 1 is offering a 30watt unit as '100% OEM Compatible' but the actual OEM part is 40W. So I'd recommend holding out for a 40W unit.