在英语中，买双新鞋可以用以下几种表达方式：

buy a new pair of shoes

这是最常用的表达方式，其中的"pair"是"双"的意思。

例句：

I need to buy a new pair of shoes for work. (我需要买一双新工作鞋。)
She decided to buy a new pair of shoes for her birthday. (她决定在生日时买一双新鞋。)
get new shoes

这种表达方式比较简单，适用于非正式场合。

例句：

I'm going to get new shoes next week. (我下周要买双新鞋。)
He needs to get new shoes before the marathon. (他在马拉松前需要买双新鞋。)
purchase new shoes

这种表达方式适用于正式场合，"purchase"是"买"的意思。

例句：

I'm going to purchase new shoes for the summer. (我要买双新夏季鞋。)
The company will need to purchase new shoes for its employees. (公司需要为员工买双新鞋。)