Substitutes:

• Coffee Liqueur: If you don't have coffee liqueur, you can use chocolate liqueur for a different flavor profile. I've also used espresso mixed with sugar syrup as a quick substitute.
• Light Rum: Aged rum or even spiced rum also work well in this cocktail. Feel free to experiment with your favorite bottles, or even with a blend of several rums!
• Vanilla Ice Cream: You can use chocolate or caramel ice cream for a different take on this cocktail. For a dairy-free option, coconut milk ice cream works great and adds an interesting twist to the flavor. 

Making a Pitcher of Hummer Cocktail:

• Scale: To make a pitcher that serves 8, multiply all the ingredients by 8. That would be 12 oz of coffee liqueur, 12 oz of light rum, 16 scoops of vanilla ice cream and approximately 6 cups of crushed ice.
• Blend: In a large blender, combine the coffee liqueur, light rum, vanilla ice cream and crushed ice. Blend until smooth.
• Serve: Pour the mixture into individual glasses Old Fashioned or rocks glasses. Add a straw, sprinkle a bit of cocoa powder on top and serve immediately.

Making it Non-Alcoholic:

• Coffee Liqueur Substitute: You can use coffee syrup, or even an espresso mixed with a bit of simple syrup, as a substitute for the coffee liqueur.
• Light Rum Substitute: Opt for a non-alcoholic light rum; these are available and reasonably mimic rum's flavor. If you’re feeling crafty, you can also make your own rum substitute by infusing together rooibos tea and a bunch of spices of your liking (vanilla, cinnamon, clove, allspice and banana are always a good way to start). Mix all the ingredients together, add hot water, cover and let it infuse for at least 3h (the stronger the better, so if you have time let it infuse overnight. In that case, you can either let it rest in the fridge once the liquid has cooled down). Give it a taste, adjust the spice level if necessary and strain it once you’re happy with the result. Stored properly (in an airtight container in the fridge), this “tea-rum” can be kept for up to a week.
• Proceed As Usual: Use these non-alcoholic substitutes instead of the regular ingredients, follow the original steps, and enjoy a non-alcoholic version.

Making it Vegan:

• Vanilla Ice Cream Substitute: Use a vegan-friendly ice cream substitute, such as almond milk or coconut milk ice cream. These alternatives work well and maintain the creamy texture of the cocktail.
• Coffee Liqueur: Just make sure that the brand you’re using is vegan friendly (Kahlua, one of the most popular options on the market, is not vegan-friendly).