China Visa on Arrival

You cannot obtain a Chinese visa on arrival, but you can obtain certain, locally limited, visas on arrival like Shenzhen, Xiamen (both 5 days) and Zhuhai (3 day) VOAs.

Please, have in mind that the price for VOA for Canadian citizens is 168, but for US citizens a steep 956 CNY is required.

My suggestion is that you disregard any VOA and use some practical 144 visa free transit option. For example, if you stay in Hong Kong, you can fly from Hong Kong to Gunagzhou, enjoy your stay in entire Guangdong province and then return by catamaran from Shekou port in Shenzhen to Macau. Like this you will be in a transit:

Hong Kong - Guangzhou - Macau

So, perfectly eligible for 144 hojur visa free trransit and able to explore entire Guangdong province visa free.

There are several other convenient options like:

Hong Kong - Beijing - Macau (everything by plane)

Also, available for 144 hour visa free transit...

Please, think about these details and options.