Hello James, do you mean buying this costume in custom size? If so, if you order custom size now (about 3 weeks making costume time and use the fastest shipping method (Premium Express, 3-6 days shipping time), it may able to reach you before Halloween, but we are unable to guaranteed that, hope you can understand. n_n
Please simply select the 'custom size' and fill up your exact body size, and our tailor will make your costume size as required.
*Custom size costume doesn't charge extra cost, but the processing time will be longer than standard size costumes; for this costume in custom size, we need about extra 1-2 weeks to make it (excluding the shipping time).